Soloing Patchwerk 25-man version was something I had been meaning to do for a while. The main reason I did not attempt it sooner was because of all the trash leading up to him. I had no idea how to handle trash re-spawning or if any of my ideas would even work. I spent a great deal of time thinking about how I would handle every aspect of the fight but I had to resolve numerous issues during the thought process and had to overcome various things which I thought would make the fight impossible. Eventually, I came up with 2 and in most cases 3 ways of handling every problem Patchwerk could throw at me. However, I also came into this fight with a technique I figured out elsewhere, a Shadowstep technique I dub Jiderstep. This technique involves an Unconscious Dig Rat (http://www.wowhead.com/item=5052) which is considered a critter and it is just like any other rat/critter in game except for the fact you can drop it where you like and it stays put and lasts until it is killed or the server is restarted. You can shadowstep to it just like any other critter. Due to the significant increase in his health pool I tested my methods successfully in 10-man before moving on to kill it on 25-man.
The fight takes places in two positions, one in the tunnel past Grobbulus, the other on the floor along Patchwerk's patrol path. The setup begins by Shadowstepping to Grobbulus on the platform he tosses his slimes from. I then go into the poison tunnel that leads to Gluth to drop an Unconscious Dig Rat at a key location inside the tunnel where there is a hole that leads back to Patchwerk's room. This position and the floor position are important as they are beyond the leash points for Grobbulus and they allow me to Shadowstep up and drop down whenever I need to. Once the Unconscious Dig Rat is in the right position I jump down and buff and get ready to pull Patchwerk. I execute the pull by pre-potting and launching a Hand-Mounted Pyro Rocket (http://www.wowhead.com/spell=54998). The use of a ranged attack to pull is important as it will require him to path all the way to that point to reset/full heal after a Vanish or Shadowmeld.
After that, the fight basically becomes a repetition involving a few key ideas. Firstly, I never engage Patchwerk without Evasion. Anytime I am attacking and Evasion is about to wear off, I either Shadowstep up to the tunnel or drop down to the floor. This forces him to spend a great deal of time pathing which enables me to wait for the Evasion cooldown and to heal myself. Another key point is using Vanish and Shadowmeld appropriately. On the initial aggro of Patchwerk, his trash is also put into combat which requires me to Vanish it off but I also use it during the fight to reset his enrage timer which eliminates the need to deal with the increased damage and slime bolts. To do this, I wait for Preparation to come back up, and then I wait until Patchwerk reaches the poison tunnel position. I jump off and immediately Shadowmeld which gets me out of combat and gives me time to eat and/or rebuff as needed. My potion timer also resets. Since I am no longer in combat Patchwerk is in evade mode and begins his pathing back from the tunnel through Grobbulus' room. This is where the pull positioning comes in to play as I am already waiting to intercept him well before his final reset point which would heal him to full. When I engage him his trash aggros again which forces me to Vanish. I watch carefully and if that Vanish fails to reset the trash I burn Preparation and Vanish again. This cycle is repeated until the boss is dead which resulted in a fight lasting 4 hours 45 minutes on my kill.
Buffs: Drums of Forgotten Kings, Drums of the Wild, Runescroll of Fortitude, Scroll of Agility VIII, Flask of Endless Rage, Blackened Dragonfin. Jewel-crafting and Engineering professions. Gear used can be viewed at http://www.wowarmory.com/character-sheet.xml?r=Stormreaver&cn=Jider&gn=Impervious. Both weapons are enchanted with mongoose and Instant poison main-hand and Deadly poison off-hand. The reason behind using Purified Shard of the Flame (http://www.wowhead.com/item=49463) was to counter the significant nature damage from the tunnel (ticks added up to ~2 million damage) and provide extra healing. Other methods of healing included eating, bandages, and Dense Stone Statues (http://www.wowhead.com/item=25883). The talent spec used was 0/18/53 and glyphs were Hemo/evasion/ghostly strike http://www.wowhead.com/talent#fZ0gqb0cZtMcdI0kdVuAcRx:oqdzmc . Besides Shadowstep, many of the talents chosen are very useful for this encounter by providing extra survivability (Enveloping Shadows, Cheat Death), increased damage (Dirty Deeds, Setup), or both (Sinister Calling, Lightning Reflexes, Endurance).
Song #1 Velvetine Safe [Wherever You Are] (Rank 1 Remix)
Song #2 Delerium Truly (Signum Club Mix)